How to get rid of double faces on my mesh?
Consider 


using Mesh/Cleanup/Limited Dissolve.  Mesh Menu in Edit Mode.
using a Mirror Modifier to keep both sides exactly the same.  This means you would delete one side, right or left and let the modifier keep the sides in correspondence.  The modifier can merge the middle vertices.
Delete the loop ring.  Then Bridge Edge loops on the two open loops which need to be closed. This is on the Edge menu.